1. Field of the Invention
The present invention relates to a surface coating film formed on a base material which is a hard material, direct or indirect there onto, a method of manufacturing thereof, a cutting tool and a cutting machine.
2. Description of the Related Art
These years, the consciousness as to environmental problems have been stimulated even in the technical field of cutting, and in particular, environmental adaptability with respect to lubrication oil has become a great issue. Accordingly, in order to reduce detrimental affection upon the environment, and further, in view of cost reductions, the need of a dry cutting technology which can completely eliminate the necessity of lubrication oil have been increased.
The merits as to a dry cutting process are as follows: occurrence of environmental problems caused by cutting oil or additives thereof can be eliminated, recycling can be facilitated, the costs caused by using and treating lubrication oil can be reduced, and so forth. Meanwhile since no lubrication oil is used, advantages obtained by lubrication, cooling and the like which have been obtained by the lubrication oil cannot be obtained, and severe cutting conditions are required.
A technology for forming a coating film having a high degree of hardness on a base material with the use of a process of physical vapor deposition has been developed so as to accept the dry cutting technology, that is, a TiN group coating film, a TiAlN group coating film or the like has been applied to a tool. However, since the TiN group coating film starts its oxidation at about a temperature of 500 deg. C. while the TiAlN group coating film starts its oxidation at a temperature of about 800 deg. C., there has been raised such a problem that these films cannot be applied to a tool adapted to be used at a high temperature.
Recently, a TiAlN group coating film disclosed in Patent Document 1 (Japanese Patent Laid-Open No. H10-25565) has been developed, which starts its oxidation at a high temperature in a range from about 1,000 deg. C. to 1,200 deg. C., and which can accept cutting conditions under a high temperature.
However, although the TiAlN group coating film disclosed in the Patent Document 1, can accept the cutting condition under a high temperature, it would soon peel off. Further, its oxidation-resistance is insufficient in the case of using it under a high temperature.